1. Field of the Invention
The present invention relates to a fuel cell module.
2. Description of the Related Art
Recently much attention has been focused on fuel cells that feature not only high energy conversion efficiency but also no hazardous substance produced by the electricity-generating reaction. Known as one of such fuel cells is the polymer electrolyte fuel cell (PEFC) which operates at temperatures below 100° C. As known types of the polymer electrolyte fuel cell (PEFC), there are, for instance, one using hydrogen as the fuel and another, called direct methanol fuel cell (DMFC), in which methanol water solution as the fuel is not reformed but is directly supplied to the anode so that electricity is produced by an electrochemical reaction induced between the methanol water solution and oxygen.
Of the PEFCs as mentioned above, the passive-type PEFCs and DMFCs which supply air as the oxidant to the cathode by natural diffusion have had a problem of their own. That is, when water produced at the cathode (air electrode) is excessive, the water covering the cathode may interfere with an adequate supply of the oxidant, such as air, to the cathode, thus leading to an output decline.
Therefore, it has been desired that methods be devised by which the water thus produced be removed efficiently without allowing it to cover the cathode. One example of conventionally known methods is a fuel cell equipped with a water retention means having water-absorbing property which is disposed in contact with an oxidant electrode and ion conductor. Another known example is a fuel cell in which water collected in pores formed in a cathode-side gas diffusion layer is led outside by a water-conducting member disposed in such a manner as to enter the pores.
However, such conventional fuel cells require extra space in the entirety of a fuel cell because it is necessary to have a water retention or water storage unit in the lateral or external part thereof. Furthermore, the conventional water-conducting member, which is provided in such a manner as to cover the whole cathode, can cause a drop in output by obstructing the diffusion of air to the cathode electrode.